.any character except newline\d \w \sdigit · word char · whitespace[abc] [^abc]character set · negated set* + ?0+ · 1+ · optional{2,5}between 2 and 5 times^ $start · end of line( ) (?: )capture · non-capturing group(?<n>…)named capture groupa|balternation(?=…) (?!…)lookahead · negative lookahead